Sample injection device

ABSTRACT

An injection port suitable for use with a hypodermic syringe in high pressure gas chromatography comprises 2 septa mounted in series in a housing. The septa are made of a material which can be penetrated by the needle of a syringe and each septa is backed by a disc of rigid material having a hole for the needle to pass through. Preferably the septa are made of silicone rubber and backed by a disc of stainless steel.

United States Patent Harding et a1.

[ 51 Sept. 26, 1972 [54] SAMPLE INJECTION DEVICE [72] Inventors: Albert Frederick Harding, 129 l-lanworth Road, Hampton; Brian Pearce, Beg Meil, Onslow Crescent, Woking; William Llewelyn Thomas, Pen Bryn, Bagshot Road, Englefield Green, Egham, all of England 221 Filed: Aug. 25, 1970 21 Appl.No.: 66,708

[30] Foreign Application Priority Data Sept. 2, 1969 Great Britain ..43,3l1/69 [52] 0.8. CI. ..73/422 GC [51] Int. Cl. ..G01n l/00,G0ln 31/08 [58] Field of Search ..73/422, 422 GC, 23.1

[56] References Cited UNITED STATES PATENTS 2,839,152 6/1958 Tracht ..73/422 GC 3,137,174 6/1964 Hawk et a1 ..73/422 GC UX OTHER PUBLlCATlONS Publication: Article, A Sample Injection Port for the Gas-Liquid Chromatographic Analysis of Irradiated Organic Compounds published in the Journal of Scientific Instruments by Barakat, 1967, Vol. 44, page 1031.

Primary Examiner-Louis R. Prince Assistant Examiner-William A. Henry," Attorney-Morgan, Finnegan, Durham & Pine 57 ABSTRACT An injection port suitable for use with a hypodermic syringe in high pressure gas chromatography comprises 2 septa mounted in series in a housing. The septa are made of a material which can be penetrated by the needle of a syringe and each septa is backed by a disc of rigid material having a hole for the needle to pass through. Preferably the septa are made of silicone rubber and backed by a disc of stainless steel.

2 Claims, 1 Drawing Figure PATENTEnsEP2s m2 INVENTORS: ALBERT FREDERICK HARDING BRIAN PEARCE SAMPLE INJECTION DEVICE This invention relates to a device and a method suitable for the injection of liquid samples into a high pressure chromatographic system.

In the field of high pressure fluid chromatography, the methods which are employed for introducing samples into the high pressure system are of three main types.

The simplest method is to introduce the sample into the column at atmospheric pressure by known means, e.g., by hypodermic syringe before assembling the column. The column is then connected to the highpressure source and the pressure is brought to the desired value.

This method suffers from the disadvantage that the column has to be depressurized before each sample introduction. There is also inevitably some loss in precision in measuring data such as retention times.

Another method is to use a sampling loop in conjunction with a by-pass system. This necessitates at least three valves for isolating the sampling loop to permit further samples to be introduced.

This method is rather cumbersome and is not very precise. Also the multiplicity of valves increases the complexity and size of the equipment and makes leaks more likely.

The remaining method is by means of pneumatic high pressure valves of suitable design. These have to be well-engineered and robustly constructed and are somewhat costly.

The method most widely used for sample introduction in conventional chromatography at atmospheric pressure is the hypodermic syringe/septum technique. The apparatus is simple and cheap, and is eminently suitable for introducing very small known amounts of liquid. However, the ordinary type of septum cannot be used at pressures much above 200 psig because the rubber septum pad does not have sufficient strength to withstand the pressure.

Attempts have been .made in the past to overcome this difficulty by backing the septum with a metal disc having a hole through which the needle of a hypodermic syringe can be inserted. However, it has been reported that the septa normally used in gas chromatography are extruded through 0.1 cms orifices at high-pressure (H.N.M. Stewart el al., J Chrom 38, 1968, 209).

It has now been found that, by employing two or more septa mounted in series, a large number of injections can be performed without leakage from the high pressure system.

Thus, according to the present invention there is provided an injection port suitable for use with a hypodermic syringe in a high pressure chromatographic system, said port comprising two or more septa mounted in series in a housing and made of a material capable of being penetrated by the needle of a hypodermic syringe, each of thesepta being in contact with a disc of rigid material, having a hole large enough to permit the passage of the needle of a syringe.

By high pressure we mean pressures above 200 psig particularly above 1,000 psig.

The septa maybe made of a wide variety of materials, e.g., natural and synthetic rubber, plastics, e.g., polyvinyl chloride, polyethylene, polypropylene,

polyesters or silicone rubber. The preferred material is a silicone rubber, e.g., a temperature resistant silicone made by ESCO (RUBBER) LTD. Each of the septa is in contact with a disc of rigid material to provide support, the disc having a hole large enough to permit the passage of the needle of the syringe. Preferably, the hole is only just large enough to admit the needle. A preferred material for the disc is a metal, for example stainless steel.

The septa are mounted in the usual way under compression, so that after being punctured they seal the hole made by the needle and prevent escape of gas without any adjustment. The injection port according to the inventior may be used at temperatures from ambient up to 250C.

According to another aspect of the present invention there is provided a method for introducing a sample into a high pressure system, for example a high pressure chromatographic system which method comprises injecting the sample from a hypodermic syringe by penetrating the septa mounted in a inlet port as hereinbefore described with the needle of the syringe, injecting the sample and withdrawing the syringe.

The injection port according to the present invention 'may also be used for withdrawing samples from a high pressure system, for example a high pressure chromatographic system. The injection port according to the present invention containing 2 septa can be used at pressures up to about 3,500 psig. For very high pressures, e.g., 4,000 psig and above, three or more septa may be mounted in series.

The double septum injection port is shown in the figure. The septa, 4, are precisely of the same type used in ordinary gas chromatography, are made of silicone rubber, and are 0.928 cms. diameter and 0.312 cms. thick. Each septum is backed by a stainless steel disc 1 of the same diameter and thickness. Holes of 0.051 cms. diameter are drilled axially through each disc; these holes are just large enough for the insertion of a 0.045 cms. diameter standard hypodermic syringe needle. The septa and discs are located in a cylindrical chamber 0.933 cms. diameter and approximately 1.27 cms. deep, drilled out of a block of metal 3 such as stainless steel having the necessary machanical strength to withstand the high pressures involved. Alternatively a 0.312 cms. internal Ermeto high-pressure tee, or equivalent fitting, may be adapted to accommodate the rubber pads and backing discs.

The injection point, 2, is provided by the hole in a locking nut. The discs and septa are held in place by the locking nut which can be tightened as required to take up leaks as they occur. The locking nut has a central hole 0.051 cms. in diameter. Also the holes in the upper faces of the locking nut and backing discs are chamfered to permit easier insertion of the hypodermic syringe needle.

EXAMPLE Samples of hydrocarbon mixtures were injected into a high pressure gas chromatographic system operated at a temperature of C and at different pressures in the range 1,800 to 3,000 psig (carbon dioxide), by perforating a double septum assembly with a Hamilton 1011.! syringe needle of diameter 0.045 cms. The two septa were made of silicone rubber manufactured by ESCO (RUBBER) LTD. and each septum was backed by a disc of stainless steel having a hole 0.051 cms. in diameter. More than 250 injections were made under these conditions. Small leaks occurred from time to time but these were easily stopped by tightening up the locking nut fractionally.

The device has also been successfully used at pressures up to 3,400 psig and temperatures up to 150C.

A single septum device comprising a silicone rubber septum provided with a backing disc having a hole 0.051 cms. in diameter was constructed and tested at different pressures in the range 1,400 2,200 psig and temperatures in the range 45 to 105C as described above with reference to the double septum injection port. It failed completely after 200 injections. It also required far more attention to prevent leaks than the double septum injection port.

We claim:

1. An injection port suitable for use with a hypodermic syringe in a high pressure chromatographic system, which port comprises two or more septa mounted in series in a housing and made of a material capable of being penetrated by the needle of a hypodermic syringe, each of the septa being in contact with a disc of rigid material having a hole large enough to permit the passage of the needle of a syringe.

2. An injection port as claimed in claim 1 wherein the septa are made of silicone rubber.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,693,455 Dated September 26, 1972 Inventor(s) Albert Frederick Harding et. a1

It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

On the cover sheet, insert [73] Assignee I The British Petroleum Company Limited, London England Signed and sealed this 2nd day of January 1973.

(SEAL) Attest:

EDWARD M. FLETCHER,JR. I ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents F ORM PO-IOSO (10-69) USCOMM-DC 60376-P69 fi u.s. GOVERNMENT PRINTING OFFICE 19w 0-a6e-a:u. 

1. An injection port suitable for use with a hypodermic syringe in a high pressure chromatographic system, which port comprises two or more septa mounted in series in a housing and made of a material capable of being penetrated by the needle of a hypodermic syringe, each of the septa being in contact with a disc of rigid material having a hole large enough to permit the passage of the needle of a syringe.
 2. An injection port as claimed in claim 1 wherein the septa are made of silicone rubber. 